Increasing Wheel Speed Research Articles

Effects of process parameters on melt-spun AgCu

Process parameters in chill block melt spinning (CBMS) play an important role in product formation during rapid solidification. The effect of variations in wheel speed and melt superheat on ribbon dimensions and microstructures of Ag-19wt.%Cu melt spun under high vacuum conditions were examined. The ribbon thickness varied linearly with (solidification time) 0.5, and the solidification rate increased with increasing wheel speed. The initial solidification microstructures had a fine equiaxed two-phase morphology on the wheel side which developed into a directional growth. Examination of serial sections parallel to the wheel side revealed a helical two-phase growth pattern in the mid-thickness of the ribbon which subsequently adopted a mixed cellular-dendritic solidification mode. The helical morphology appears to be related to the morphological instability associated with a banded microstructure. Near the free surface an equiaxed microstructure again developed as a result of dendritic fragmentation induced by melt shear flow. Wheel speed and melt superheat affected the extent of the different microstructures. Through control of processing parameters in CBMS, under high vacuum conditions, a degree of control on ribbon dimensions and structural development has been achieved.

Magnetostriction of the rapidly quenched Co80Nb8B12 alloy: Dependence on quenching rate, structural relaxation, and temperature

Ribbons of nominal composition Co80Nb8B12 have been prepared by the single roller quenching method using different wheel velocities ranging from 26 to 42 ms−1. X-ray diffraction patterns for ribbons prepared at low velocities show crystalline peaks but characteristic for the amorphous state for samples prepared at velocities above 36 ms−1. Room-temperature values of the magnetostriction constant λs depend on the quenching rate and changes from 4×10−7 to −1×10−6 as the wheel speed increases. Zero magnetostriction samples are obtained at about 34 ms−1. Thermal treatments change the values of the magnetostriction in the same way as a decrease in the quenching rate does. A dependence of the magnetostriction constant on the applied stress has been found. This dependence, fully reversible, is observed at room temperature.

Microstructure and stability of melt spun INCONEL 713 LC

The alloy IN-713LC* was used in an investigation of the effect of process parameters on the microstructure of a rapidly solidified melt-spun material. The resultant ribbon microstructure consisted of several distinct regions, each of which corresponds to a different thermal history during processing. A chill zone of equiaxed randomly-oriented grains exists in a region of the foil which was in contact with the wheel during casting. This zone develops into a dendritic growth morphology with distance away from the lower ribbon surface. Dendrites inclined in the direction of wheel rotation result from growth into a flowing stream. TEM studies showed that a cell structure formed, the cell size decreasing with increasing wheel speed. Aging studies indicated that the cell structure plays an important role in γ’ precipitation. Results relating to heat treatments (as would be encountered in compaction and use) and the stability of the melt-spun structure are considered.

Photocalorimetric cooling rate measurements on a Ni-5 wt% A1 alloy rapidly solidified by melt spinning

Binary Ni-5 wt%Al alloy ribbons have been rapidly solidified by melt spinning and their cooling rates measured by a photocalorimetric method in which photographic colour density is calibrated against ribbon temperature. The cooling rates have been measured as a function of melt spinning process parameters such as wheel speed, gas ejection pressure and melt superheat. Heat transfer coefficients and Nusselt numbers have been calculated from the measured cooling rates using both Newtonian and non-Newtonian heat flow analyses. Cooling rates during melt spinning are found to be in the range 1.105–5.105 Ks−1, and increase linearly with increasing wheel speed, with relatively little effect of varying gas ejection pressure or melt superheat. Heat transfer coefficients and Nusselt numbers are found to be in the range 6.104–2.105 Wm−2K−1 and 0.07–0.2 respectively. The increase in cooling rate with increasing wheel speed results partly from a decrease in melt spun ribbbon thickness and partly from an increase in heat transfer coefficient caused by improved thermal contact between ribon and wheel.

Amorphous ribbon formatin and the effects of casting velocity

Experimental relations between melt puddle length and ribbon thickness in the steady state spin casting of Fe 81.5B 14.5Si 4 amorphous ribbons are analyzed with a continoues casting model to estimated the ribbon formation temperature T t and the metal-wheel interfacial conductance h. The result T t ≈ 1000 ° C indicates that a high viscosity liquid layer contributes to the final ribbon thickness about as much as the amorphous solid layer defined by the isotherm T g = 450 ° C. It is also shown that T t remains constant but that h increases from 12 to 50 cal cm −2 s −1 K −1 with increasing wheel speed. The improved h value at higher casting speeds results from better melt-wheel contact as revealed in the contact pattern on the wheel-side surface of the ribbons.

高速研削の研究

The influence of the increase of wheel speed on the grinding results has been studied experi-mentally. In this cylindrical grinding tests, the wheel speed was increased up to 3500m/min from 1300m/min. The following results are obtained : 1. As the wheel speed is increased, the ground volume per unit time increases and so the practical reduction of work radius versus the theoretical reduction of work radius increases.2. The relation between the grinding force (P) and the wheel speed (V) is Poc (1/V) 0.791.47. And as the grain size of wheel is smaller, the value of the index of this formula is larger.3. The other result of higher wheel speed is the improvement of the surface finishing of the workpiece by decreasing the thickness of chip.4. The influence of the higher wheel speed is smaller to the heat resisting steel as like the high vanadium high speed steel than to the carbon steel.5. At the high speed grinding, an inclined metal sheet must be fixed against the wheel in order to deflect the air-flow on the rotating grinding wheel which prevents the coolants from penetrating into the grinding zone.

カップ形砥石による円筒研削の研究(第2報)

In this report, the relation between the finished surface roughness and the grinding conditions on the cylindrical grinding operations by the cup type grinding wheel was studied experimentally.The results obtained are as follows;(1) The ground surface roughness decrease to increase of wheel speed, width of the wheel and number of traversing, and to decrease of depth of cut, surface speed of the workpiece and traversing speed. Furthermore, the surface roughness becomes smaller under the following conditions, i.e. an average diameter of the wheel: 70100 mm and an average crosshatch angle: 2080°(2) The form factor of the finished surface becomes large value when the average crosshatch angle (φm) are as follows;axial direction: φm≅40°circumferential direction: φm≅180°(3) The ratio of the surface roughness (roughness of circumferential direction/roughness of axial direction) is increase to decrease of the crosshatch angle, and that ratio become 1 when an average crosshatch angle is apporoximately 90°, and the surface of non-directional roughness is produced.